Continuous beta cell cultures are needed for quantitative controlled experiments to: a) elucidate the mechanisms of insulin biosynthesis and secretion; b) evaluate the immunological characteristics of beta cell constituents; and c) determine the mechanisms whereby specific cytotoxic chemicals and viruses damage beta cells selectively. Long-term maintenance, continuous passage, and the bulk propagation of pancreatic islet cells "in vitro" have been hampered thus far by the limited replicative ability of the normal beta cell. We will establish reproducible animal models for induction of hyperplasia and transformation of the beta cell to establish permanent lines of insulin-producing cells in tissue culture. Weanling rats and inbred mice will receive injections of cortisone and gold-thio-glucose to induce hyperplasia of the beta cells. Rodents then will be administered ionizing irradiation and streptozotocin-nicotinamide. To detect hyperplastic and neoplastic changes in beta cells, blood from treated animals will be monitored at intervals for glucose and assessed by radioimmunoassay for elevated levels of insulin. Hyperplastic and transformed islet cells will be isolated selectively using: 1) differential attachment; 2) affinity columns; and 3) colloidal silica density gradients. Stimulation and establishment of beta cell lines will be encouraged in vitro by use of complex media containing inhibitors for fibroblasts. The identification and assessment of the functional status of cultured beta cells will be done by aldehyde thionin and immuno-peroxidase staining, transmission electron microscopy of cultured cells, and radioimmunoassay to detect insulin release into the medium.